What the WHO limits are, and are not
The World Health Organization publishes lower reference limits for semen: the 5th centile of a large group of men whose partner conceived within a year. The 6th edition, published in 2021, changed several limits from the 2010 edition: volume down to 1.4 mL from 1.5, concentration up to 16 million/mL from 15, total motility up to 42 percent from 40, progressive motility down to 30 percent from 32, and vitality down to 54 percent from 58. Being below a limit means being in the bottom 5 percent of fertile men, which is worth investigating but is not a diagnosis of infertility. Being above every limit does not guarantee fertility either: DNA fragmentation, antibodies and function are not measured on a standard analysis.
The number clinics actually use
Fertility clinics rarely act on a single WHO parameter. They multiply volume, concentration and progressive motility to get the progressively motile sperm count (often written TMSC or TPMC on reports), the number of forward-moving sperm in the sample. Above about 20 million, semen is unlikely to be the limiting factor and attention turns to timing and the partner's cycle: the best time to get pregnant calculator and ovulation test calculator are the useful next tools. Between 5 and 20 million, IUI is an option and success falls as the count does. Below 5 million, IVF with ICSI, where one sperm is injected into each egg, gives the best chance per cycle, and the BMI calculator for IVF covers one of the first things a clinic checks on both partners.
Why one sample is never enough
Sperm production takes about 74 days, plus a couple of weeks in transit, so a sample reflects the last three months. A fever, a course of antibiotics, a heavy week of drinking or a short abstinence interval can all pull one sample below the limits. NICE guidance is to repeat an abnormal analysis three months later, or sooner if the count is very low or zero. Two samples below the limits is the point to ask for a referral. If a repeat is normal, the first one was noise.
Questions worth asking the clinic
- Which edition of the WHO manual do your reference limits follow?
- What was the total motile sperm count, and what threshold do you use for IUI?
- Was morphology assessed by strict criteria?
- Should we check hormones (FSH, LH, testosterone) or examine for a varicocele?
- Is a DNA fragmentation test useful in our situation, or not yet?
Frequently asked questions
What is a normal sperm count?
WHO's 6th edition (2021) lower reference limits are 16 million per mL for concentration and 39 million per ejaculate for total sperm number. These are the 5th centile of men who fathered a child within 12 months, so 95 percent of fertile men are above them. A result below the limit lowers the chance per cycle; it does not mean conception cannot happen.
What is a normal sperm motility?
At least 42 percent total motility (any movement) and 30 percent progressive motility (moving forward) under the 6th edition. Older reports using the 2010 5th edition quote 40 and 32 percent. Progressive motility matters more than total.
What is a normal sperm morphology?
4 percent normal forms by strict (Kruger or Tygerberg) criteria. That sounds low because strict criteria are strict: in fertile men most sperm are classed as abnormal. Morphology alone is a weak predictor and is rarely acted on when count and motility are normal.
What is total motile sperm count and why does it matter?
Volume times concentration times motility, which gives the number of moving sperm in the whole sample. Most clinics count only the progressively motile (forward-moving) sperm, and that is the figure this calculator bands: above about 20 million is treated as normal, 10 to 20 mildly reduced, 5 to 10 the range where IUI success falls, and under 5 million the range where IVF with ICSI is usually discussed. Thresholds vary between clinics.
My results were below the limit. What happens next?
A repeat sample after about three months, because sperm take around 74 days to develop and one sample varies a lot with illness, fever, stress and abstinence time. If the repeat is also below the limits, NICE recommends referral to a fertility clinic, where a physical examination, hormone tests and sometimes a scrotal ultrasound look for treatable causes such as a varicocele, infection, or a hormonal problem.
Can lifestyle changes improve a semen analysis?
Some, within limits. Stopping smoking, keeping alcohol moderate, losing excess weight, avoiding anabolic steroids and testosterone supplements (which switch off sperm production), and avoiding prolonged heat to the testicles (hot tubs, saunas, a laptop on the lap) all have some evidence; the case for loose underwear specifically is weak. Antioxidant supplements have weak evidence. Changes take a full three-month cycle to show in a sample.
How is the sample supposed to be produced?
After 2 to 7 days of abstinence, by masturbation into a sterile pot, without lubricant or a standard condom, and delivered to the lab within an hour, kept at body temperature. A sample that missed any of these is not comparable to the reference limits and is usually repeated.
Sources
- WHO laboratory manual for the examination and processing of human semen, 6th edition - World Health Organization, 2021.
- Fertility problems: assessment and treatment (NG257) - NICE, 2026.
- Infertility: diagnosis - NHS.
- Evaluating infertility - ACOG.
These calculators give estimates based on cycle averages and standard formulas. They are for general information only and are not medical advice. For anything concerning your health or pregnancy, talk to a qualified healthcare provider.